A calculator that doesn't round (constructive-calculator.dimview.org)

Author here. I could not find a constructive‑reals calculator on iPhone, so I ported the engine Android uses: Hans Boehm's com.hp.creals plus AOSP's UnifiedReal/BoundedRational. Used Opus 4.8 to do the port and Fable 5 for the review.

Fable 5 caught a couple of real concurrency bugs the port introduced while adapting Java's synchronized/AsyncTask to Swift concurrency, including one that was a memory‑safety bug on shared singletons like π, not just a wrong digit. None would have shown up in the unit tests. Writeup has the details.

It's an early iPhone TestFlight beta (link in the post); happy to go deep on either the constructive‑reals side or the AI‑assisted‑dev side.

Very interesting, thank you for posting! I'm curious - roughly how many tokens do you think you used during the initial port and subsequent bug hunting and fixes?

It would also be fun to have a full computer algebra system (like maxima) on a phone

Edit: Whoops. My bad. This must have been a HN "second chance" winner.

btw if you turn the iphone calc into landscape mode and switch you scientific calc it does Ramanujan's constant without rounding, but stops after the twelve 9s.

> Hans Boehm built a Java library for this in the 1980s and 90s

Hans is such a prolific programmer that he wrote a Java library before Java was even invented?

I don't get why this is a big deal. All the calculators I've used have been rectangle.

> I built one, by porting Boehm’s engine. > It’s 2026, so I didn’t hand-write the port. I directed Opus 4.8 to translate the source line by line into Swift

I wish I could filter out stuff like this. Cool work by Hans Boehm, but what's the value add in this blog post.